Stroke is the third most common cause of death in North America with approximately 750,000 new strokes reported annually, of which 150,000 are fatal. Approximately 75% of strokes occur in the distribution of the carotid arteries. Among those, a thrombotic etiology (carotid occlusive disease) is one of the most common causes. Recently published studies have shown that patients who underwent carotid stenting in combination with a cerebral protection device had better overall outcomes as related to stroke, death and MI as opposed to carotid endarterectomy. What is not known is whether protection devices which allow some particles (100 micron particle size or less) to pass through the filter or particles that embolize during placement or removal of the protection device, will have any delayed abnormal outcomes as determined by neuropsychological testing.